Mix the yolks, sugar, vanilla sugar and hot water until frothy. Add the oil, nuts and chocolate. Fold in the flour, baking powder and egg whites. Bake at 160 ° C (hot air) for about 20 to 25 minutes.
While still warm, pour a shot of rum over a cup of coffee. Whip 2 cups of cream until stiff, sweeten slightly, spread on the cold cake. Pour eggnog in a plastic bag, cut off a small corner and pour the eggnog in a grid shape over it and sprinkle with roasted almond slivers.